China on Thursday said it deeply regretted the US decision to ban American banks from dealing with Banco Delta Asia after concluding that the Macao bank had helped North Korea launder money.

The ban by US Treasury will test whether Pyongyang will follow through on last month's agreement to dismantle its nuclear programme, but also paves the way for the bank to release a portion of the $25m in North Korean assets that was not related to illicit activity.

"We have expressed our deep regret to the US side," foreign ministry spokesman Qin Gang told reporters in a regular briefing in Beijing.

Boomberg news agency also quoted him as saying: "We believe the US side should take actions that help stimulate progress in the six-party talks and help in maintaining social stability of the Macao Special Administrative Region."

North Korea has demanded that the US lift what it terms the financial "sanctions" imposed on its regime. The US Treasury designated Banco Delta Asia as a "prime money laundering concern" in 2005. That sparked a run on the bank, which resulted in the Macao government taking control of the family-owned institution and freezing $25m in North Korean assets. The Macao government has also launched its own investigation, but has yet to reveal its findings.